Sound reproducing technologies of mobile multimedia have been developed along with mobile communication technologies, which require high performance, high sound quality, and high output of a microspeaker.
In most cases, a conventional microspeaker does not employ a suspension so as to achieve a light weight of a diaphragm, and a lead wire of a voice coil is bonded to the diaphragm so that external electrical signals can be applied to the voice coil. Thus, a partial vibration often occurs due to the absence of the suspension, and the lead wire of the coil is often down due to a tensile force in high outputs, which makes it difficult to use the microspeaker in high output applications.
In order to solve the foregoing problem, a microspeaker has been suggested that uses a suspension made of an FPCB with a conductive pattern for transferring electrical signals. FIG. 1 shows a general suspension made of an FPCB, wherein a conductive film 20 made of copper or the like is disposed on a base film 10 made of a PI having good thermal properties, and a cover layer 30 is attached thereon to protect the conductive film 20. In addition, the base film 10, the conductive film 20 and the cover layer 30 are attached to one another by means of adhesives 41, 42, 43 and 44.
With respect to the microspeaker using the suspension, an increase in weight of the vibration system, which results from the application of the suspension, causes a decrease in sound pressure of the microspeaker. Additionally, cracks may be formed on the conductive film 20 in high outputs, which leads to defects. In order to prevent a decrease in sound pressure, it is possible to reduce the weight of the vibration system by appropriately adjusting the shapes of the cover layer 30 and the conductive film 20 of the suspension. However, as the diaphragm gets thinner, a local vibration mode of the diaphragm occurs in high frequency regions, to which has a detrimental effect on sound properties. Therefore, it is necessary to appropriately adjust the shapes of the cover layer 30 and the conductive film 20 to prevent such a local vibration mode.